The systemic administration of drug agents, such as by transoral or intravenous means, treats the body as a whole even though the disease to be treated may be localized. In such a case, systemic administration may not be desirable because the drug agents may have unwanted effects on parts of the body which are not to be treated, or because treatment of the diseased part of the body requires a high concentration of drug agent that may not be achievable by systemic administration.
It is therefore often desirable to administer drug agents at localized sites within the body. Common examples include cases of localized disease (e.g., heart disease) or occluded body lumens. Various methods have been proposed for such localized drug administration. For example, U.S. Pat. No. 5,304,121, which is incorporated herein by reference, discloses a method of delivering water-soluble drugs to tissue at desired locations of a body lumen wall. The method generally includes the steps of impregnating a hydrogel polymer on a balloon catheter with an aqueous drug solution, inserting the catheter into a blood vessel to a desired location, and expanding the catheter balloon against the surrounding tissue to allow the release of the drug.
One of the potential drawbacks to conventional drug delivery techniques using drug-impregnated polymer coatings on balloon catheters is the possible premature diffusion of the drug out of the coating during delivery into the body. Two solutions to this problem have been proposed: the use of a removable sheath over the polymer coating, and the use of a dissolvable or meltable temporary coating over the polymer coating to protect and retain the drug agent in the coating prior to a time of desired administration at a target location. The sheath approach, however, adds considerable profile to the balloon catheter device, making access to small body lumens difficult or impracticable. Furthermore, the use of a temporary protective coating over a drug-impregnated polymer coating may place undesirable time constraints on the drug delivery procedure. Moreover, it is difficult to identify or develop temporary coatings that permit the release of the drug in a consistent and predictable manner.
In view of the potential drawbacks to conventional drug delivery techniques, there exists a need for a device and method for the controlled, localized delivery of drug agents to target locations within a mammalian body while avoiding the premature release of drug agent during delivery.